Heating apparatus



Nov. 17, 1942. K. F. THORNTON HEATING APPARATUS Filed Aug. 10, 1940 INVENTOR Kirby F Tho/i017 ATTORNEY Patented Nov. 17, 1942 HEATING APPARATUS Kirby F. Thornton, New Kensington, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Application August 10, 1940, Serial No. 352,092

3 Claims.

This invention relates to means for heating material in preparation for hot working operations, and particularly relates to the provision of means for the heating of non-ferrous metal rivets such as aluminum alloy rivets having di- 9 mensions or other physical characteristics which necessitate hot driving.

The invention is hereinafter described in connection with the heating of aluminum alloy rivets, a purpose for which it is particularly well which will quickly and accurately bring the material to be hot formed to the desired temperature Another object is to provide a heater I which is of simple construction and which is suited and in which it will probably find its.

greatest utility though it is obviously suitablefor the heating of cylindrical non-ferrous metal articles which are to be subjected to hot forming operations of various types.

The heating of strong alloy aluminum rivets has presented special problems due to the fact that strong aluminum alloys generally develop their maximum physical properties only after rigidly controlled heat treating procedures. The most commonly used heat treatable strong aluminum alloys develop their maximum physical properties after being heated to a certain temperature, which may vary for the different alloys, followed by a rapid cooling or quenching operation, and usually acquire their maximum physical properties after the described heat treatment upon aging for a suitable period either at room temperature or reasonably elevated temperatures depending upon the particular alloy.

The maximum physical properties of these a1- loys can only be obtained by rapid cooling from a critical temperature range, which in the preferred practice for most alloys does not vary plus or minus 10 F. from a given temperature. For example, one strong aluminum alloy commonly used for rivets should be heated to a temperature of 940 F., plus or minus 10 F. to obtain the maximum physical properties. The rapid cooling or quenching necessary to complete the heat treatment is obtained by the contact of the heated rivet with the cold metal, in which it must be immediately driven, and with the riveting tools,

To obtain the necessary accurate temperature 1 control, strong aluminum alloy rivets have usual- 1y been heated by immersion in molten salt or lead baths. The inconveniences encountered in the employment of this method of heating requires no elaboration, but no other satisfactory means of heating have been developed for this purpose up to the date of the present invention in spite of many efforts to develop such means.

It is an object of the present invention to provide heating means for the described purpose 55 readily portable and can be placed in close proximity to the forming tools and the work. A still -further object is to provide heating means which ,are adaptable to heating objects of generally cylindrical shape and of varying diameters by conduction without mechanical adjustment to compensate for difference in dimensions. Other objects will be readily apparent from the following description and the accompanying drawing, in which:

Fig. 1 is an end elevational view partly in section of a' heater device incorporating the improvements of my invention with the forward door removed to better illustrate the structure;

Fig. 2 is a side view thereof partly in section and partly in elevation;

Fig. 3 is a detailed view on an enlarged scale of a portion of the heater block of Fig. 1;

Fig. 4 is a side view thereof; and

Fig. 5 is a view taken on the line V-V of Fig. 4.

The present invention consists generally in the provision of means for effecting the heating of the material to be hot formed by conduction from a heated body of material of high thermal conductivity with which it is in tight-pressed contact to obtain a rapid and uniform transfer of heat. When the material to be heated is aluminum or aluminum alloy, the heating means employed are preferably constructed principally of aluminum which, because of its highthermal conductivity, is suitable for the purpose. In the embodiment of the invention shown in the drawings, the heating means comprise a plurality of aluminum sections I and electrical resistance heaters 2 of the enclosed ribbon or strip type clamped in tight-pressed engagement by bolts 3. This entire clamped assembly will hereinafter be referred to as the heating block.

The heating block illustrated is built up of a plurality of parts, but it is apparent that for the purpose of this invention an equivalent structure could be made by casting the aluminum portion of the structure around suitably selected electrical resistance elements. It is essential, however, that the resistance elements should be so selected and disposed in the structure that it can be quickly heated to a uniform temperature over its entire area when the heating elements are connected with. a suitable source of electrical current.

The heating block is provided with a plurality of vertically elongated apertures 4 of uniform cross section extending inwardly from the front face of the block for the reception of the shanks of the rivets to be heated, the apertures being uniformly spaced and arranged in vertical and horizontal rows. These apertures extend entirely through the block and have relatively inclined downwardly converging plane side walls or surfaces 5 forming an acute angle therebetween and joined in the form shown by top and bottom walls formed on arcs of unequal circles. The maximum width of the apertures is preferably slightly greater than the shank diameter of the largest rivet to be heated and the minimum width thereof is slightly less than the shank diameter of the smallest rivet to be heated. Accordingly,-

the side walls 5 are elongated in a vertical direction in order to accommodate and support a predetermined range of rivet sizes therebetween for heating, and obviously any range of rivet sizes can be accommodated for heating under the same heating conditions by extending the inclined side walls 5 upwardly.

The heating block preferably is built up of a pluarlity of pairs of sections l arranged in vertically stacked relation and a desired number of such stacked sections assembled in side-byside relation with the electrical resistance heaters 2 conductively disposed therebetween and at the outer sides of an assembled unit. Each of the sections i is preferably formed by extrusion and provided with a recess along one lateral face thereof so that when two sections are brought together with their recessed faces abutting, the longitudinally extending apertures 4 will be formed thereby. The upper and lower edges of each extruded section are formed with an undercut groove 6 and a tongue 1, respectively, so that any desired number of such sections can be brought into vertically assembled position merely by sliding the tongue of one section in the undercut groove of another section which insures heat conducting connection between the sections.

Horizontally, any desired number of such apertured sections l and heaters 2 can be assembled together and the assembly maintained by means of the clamping bolts 3 which extend in transverse directions through the units as thus assembled. At each side of the unit, a bracket 8 is provided through which the clamping bolts I extend and by means of which the heating block is supported on insulating strips 9 that extend longitudinally through a suitable enclosure or casing Hi. The casing I preferably is composed of double walls in spaced relation and filled with suitable insulating material, and the chamber formed thereby is open at both ends. Insulated doors i l and I! are provided for closing the ends of the chamber, which doors are pivotally connected to the casing by means of hinges ii. The casing is supported on suitable legs I4 so that the heating device may be maintained at a convenient working height.

The outwardly turned legs on the lower ends of the brackets 8 are secured to the members 0 by means of bolts i that extend downwardly through the bottom wall of the casing ll, sleevelike spacers 16 being provided between the spaced walls of the casing to reinforce such walls.

The doors H and ii are provided at each side thereof with inwardly extending and accurately shaped wings H which serve to counterbalance the doors sufficiently to maintain them in closed position. At their inner ends the wings II are provided with lugs it which cooperate with stops i9 secured to the inner wall of the casing N at the upper outer corners of the chamber therein and against which the lugs 18 may abut to hold rivets into the apertures 4 from either end of the block. By this arrangement the rivets at one end of the heater can be brought up to the required temperature while heated rivets can be removed one by one from the other end of the heater for use as required.

The heating block is intended to be used with the longitudinal axes of apertures 4 in a substantially horizontal plane so that when the rivet shanks are inserted into the apertures, the shanks will rest their full length on the inclined surfaces 5. The heads of the rivets preferably abut against the face of the heating block. The included acute angle formed by the inclined surfaces 5 is so selected that the surfaces 5 will vertically support and radially confine a rivet shank therebetween for expansion into tight-pressed engagement with said surfaces when the heating operation is performed in the following manner reference being had particularly to the heating of aluminum alloy rivets. The heating block is first brought to and maintained at the desired temperature by an suitable well-known automatic temperature regulating mechanism for controlling the supply of electric current to the resistors 2. The shanks of the cold rivets are introduced axially into the apertures 4 and allowed to come to rest upon the inclined surfaces of the apertures and become somewhat loosely supported therebetween along their entire length by virtue of their weight.

As the rivets are heated. the radial expansion of their shanks against the confining side walls 5 produces a substantially continuous tightpressed contact therebetween, so that the flow of heat into the rivet shanks for diffusion therein is eifected by conduction along the entire length of the rivet shanks. It has been found that without such a pressure condition, the rivets are not heated at the same rate at all points along their shanks due, perhaps, to non-continuous contact by reason of superficial irregularities, and the whole body of the rivet shank brough into a uniformly heated condition unless the heating period includes a "soaking" period to permit diffusion of the heat entering the shanks by conduction at those points of contact that may be obtained normally in the absence of a predetermined pressure condition. However, by utilizing the thermal expansion of the rivet shanks to establish substantially continuous pressure contact against the side wall 5, the entire length of the rivet shanks receives heat from the heating block by conduction so that a uniformly heated condition in thy whole body of the rivet shanks is produced in ,a minimum time. In addition, by reason of the angularity of the side walls, the dual lines of contact of the rivet shanks therewith are located near the diametral plane of the rivets normal to the vertical axis of the apertures, whereby the body of the rivet shank is substantially vertically divided with respect to the lines of heat infusion, thereby insuring rapid diffusion of the heat throughout the cross sectional area of the rivet shanks. particularly in the heating of rivets of large shank diameter to the required temperature. Thus, knowing the length of time required to bring any rivet of a given size to the desired temperature, it is possible to effect the uniform heating of any'desired number of rivets without the necessity for determining the exact temperature of each individual rivet. This uniformity of control is obtained because of the uniform conduction of heat from the heating block to the rivets due to the substantially continuous pressure condition established therebetween.

It has been found that, in order to obtain the best results by this method of heating, the included angle between the inclined surfaces of the aperture should be between 14 and 30. If the included angle is greater than 30 by any considerable amount, the rivets will tend to ride up the inclined surfaces as they expand, and a satisfactory substantially continuous pressure contact will not be obtained and a longer heating period will be required to bring the rivets up to the desired uniform temperature. If the included angle is less than 14, there will be danger of the rivet binding or freezing which will make it quite difiicult to remove the rivets from the heater when they have reached the desired temperature because they expand into too tight engagement with the inclined surfaces. For the aluminum alloy rivets specifically referred to hereabove,. an included angle of about 24 between the inclined surfaces has been found to insure good thermal contact without binding, and the rivets can be readily removed from the apertures after loosening by a slight tap on the head of the rivet with the rivet tongs. Entirely aside from the possibility of effecting tight pressed engagement with various types of rivets, an included angle between the inclined surfaces 5 of between 14 and 30 is desirable because the points of contact of the rivet shank with the heating surfaces should be as nearly diametrically opposed as possible to insure uniform and rapid heating without obstructing removal of the rivet. The planular form of the surfaces 5 provides the same heating action for a wide range of rivet sizes.

One of the outstanding advantages of employing extruded sections for forming the heating block resides in the fact that the walls of the apertures I will be quite smooth without requiring machining operations so that when the rivet shanks are introduced therein, they will have substantially a uniform line contact with the walls of the apertures, thereby assuring rapid and uniform heating by direct conduction of the heat from the block to the shanks of the rivets. Also, the capacity of the heater block can be readily increased or decreased by adding or removing sections as required for most eiiicient operation, and servicing of the unit is facilitated.

With a heater constructed in accordance with the foregoing description provided with automatic temperature regulation, it has been possible to hold the temperature of the heater block at the highest temperature within the heat treating range of a specific aluminum alloy. namely 950 F., and uniformly heat three-fourth inch diameter rivet. within the permissible tempera-- ture range 01' 930 to 950 in a period of about four minutes.

I claim:

1. Rivet heating apparatus comprising a heating block consisting of a plurality of pairs of metal sections, said pairs being arranged in vertically stacked contacting relation and the stacked pairs disposed in side-by-side relation, electrical resistance heaters disposed between said stacked pairs and at the outer sides of the outside stacks, means for clamping said stacked pairs and said heaters in assembled relation, the abutting face of each ection of each pair being recessed from end to end to form an aperture therebetween for the reception of the shank of a rivet to be heated at either end thereof, each aperture having top and bottom walls and plane side walls inclined toward each other continuously from top to bottom and forming an acute angle therebetween of 'about 14 to about 30, said rivet shank being vertically supported and radially confined at rest axially between said side walls for radial expansion into substantially continuous tight-pressed contact therewith as it becomes heated, the vertical length of said side walls being greater than the maximum width of each aperture and said side walls constituting the major portion of the wall area of the aperture.

2. Apparatus for heating aluminum rivets of the type described, comprising a heating block provided with a plurality of apertures of uniform cross sectom arranged in vertically and horizontally spaced rows, means for heating said block, eacn or said apertures having downwardly converging plane side walls defining the manor portion or the perimeter of the aperture and forming an included angle of about 24 therebetween, said heating means being disposed in said block between the vertical rows of apertures and in spaced relation to said side walls, said side walls vertically supporting and radially confining the shank of a rivet at rest axially therebetween, for radial expansion into substantially continuous tight-pressed contact therewith as it becomes heated.

3. Rivet heating apparatus comprising a heating block and means for heating said block, said heating block being provided with a plurality of vertically elongated apertures of uniform cross section, each aperture having top and bottom walls joined by downwardly converging plane side walls constituting a greater part of the wall area of the aperture than the top and bottom walls, said side walls being disposed in an acute angle relation operable to radially confine and vertically support the shank of a rivet disposed at rest axially therebetween with the axial lines of shank contacttherewith located adjacent to the diametral plane of the rivet normal to the vertical axis of the aperture, said rivet shank expanding into substantially continuous tightpressed contact with said side walls as it becomes heated.

- KIRBY F. THORNTON.

I CERTIFICATE OF CORREGTI ON Patent 110. 2, 502,557. Nove mber 17, 191m,

7 KIRBY F. THORNTON;

It is hereby certified that error appears in the printed'agao ifiootion of the above numbered patent requiring correction as follows: Page 2; first column, l1ne 7 5, for "accurately" read -arouately-q page. 5, second col umn, line 1h, claim 1, for "ection' read: "sectionline 35, claim 2,

for "sectoin" read sectiorF-yand that the said Letters Patent should be i ead with fllis-oorreqtion therein that the same w co 0rd of-flae case 111i tbs Pgtentbffioe. si a and sealed. this 29th da r December, A. n. 15!;2.

Henry Van Arsgiale,

Adting commiasionor of Patents.

(Seal) nfom' tolthe, recll. CERTIFFICATE OF CORRECTION.

Patent No. 2, 502,3 7. November 17, -19u2.

KIRBY F. monm'on;

It is hereby certified the}: error appears in the printedsugecjiiceizion 0f the above numbered patent requiring oorpeetion as follows: Page 2.5 first column, l1ne 75 for "accurately" read -,-ar'euate 1y--; page, 5, second c01- 1mm, lineillh, claim 1, for "action" 'read' -sect1online 35, claim 2,

fo'i' "sectoin" read section'-;.and that the said Letters Patentehould be read with thiseorreqtion therein that the same flay confoim' to .the.rec-

0rd of -the case 111i Petent office. A Signed md sealed. this 29th day of December, A. n. 19!;2.

Henry van Ars'giale, (Seal) AGting Commissioner of Patent a. 

